1. Field of the Invention
The invention relates to a metal carrying sleeve for printing and transfer forms. The initial form of the sleeve is a rectangular, thin-walled flat sheet, which is shaped by bending into the desired hollow cylindrical form, and the edges of the flat sheet which point toward one another are connected permanently together.
2. Description of the Prior Art
It is known today from flexographic printing to place sleeve-type printing and transfer forms on galvanically-produced nickel sleeves. Printing and transfer forms produced in this manner can be slipped by means of pressurized air over a printing cylinder core in the known manner and affixed thereto by shutting off the air supply. Carrying sleeves of fiberglass-reinforced plastic and even of carbon-fiber-reinforced plastic are also used for this purpose. However, it is relatively expensive to use materials such as nickel and fiberglass-reinforced plastic or even carbon-fiber-reinforced plastic for producing carrying sleeves.
German Patent Application P 41 40 768 discloses a sleeve-type offset printing form produced from a rectangularly-cut metal plate, wherein the edges of the plate pointing toward one another are connected by a welded seam. The carrying sleeve produced in this manner is coated and exposed on all sides except for the welded seam.
DE 42 17 793 C1 discloses a sleeve-type offset rubber blanket that is also produced from a cut base plate, to which, while it is flat, a rubber coat is applied, and wherein the beginning and the end of the base plate, along with the rubber coat, are welded together.
Using these sleeve-type printing and transfer forms, it is possible to print in a channel-free fashion,but not continuously, i.e., only finite printing products can be produced. Until now, the use of a continuous offset printing form has not become known.
Accordingly, it is an object of the present invention is to provide relatively economical carrying sleeves for printing forms and transfer forms, with which continuous printing is possible.
Pursuant to this object, and others which will become apparent hereafter, one aspect of the present invention resides in a metal carrying sleeve for printing and transfer forms, the initial form of which is a rectangular, thin-walled flat sheet. The sheet is bent into the desired hollow cylindrical form and the edges which point toward one another are permanently connected together. The sleeve surface is processed in order to form a homogeneous outer surface so that continuous printing can be carried out. This represents an advantageous alternative to nickel, fiberglass-reinforced plastic and carbon-fiber-reinforced plastic sleeves from both ecological and economic points of view and, in addition, can be used universally for various printing methods.
The production costs for a welded precision sleeve processed according to the invention are many times lower than the production costs for galvanized nickel sleeves or coiled carrying sleeves of fiberglass-reinforced plastic or carbon-fiber-reinforced plastic, especially since it is becoming increasingly difficult to produce nickel sleeves galvanically, because this production method is accompanied by heavy environmental pollution.
Furthermore, in an additional embodiment of the invention, the carrying sleeves are produced from aluminum, steel, high-quality steel, copper or brass, depending on the particular intended use.
In another embodiment of the invention, the entire sleeve surface, including the connecting seam which connects together the edges of the sheet, is chemically roughened, anodized and provided with a final photosensitive coat so that the entire sleeve surface can be used for offset printing. In still a further embodiment of the invention the entire surface of the sleeve, including the connecting seam, is provided with a water conducting coat. This also permits the entire sleeve surface to be used for offset printing.
For use in gravure printing, the entire sleeve surface, including the coating seam, is provided with an engraved copper coat.
In yet a further embodiment of the invention the entire sleeve surface, including the connecting seam, is covered with an endless rubber coat. This arrangement is suitable for use with a transfer form.
In still another embodiment of the invention the carrying sleeve is configured so that it can be used directly as a carrying sleeve of a flexible printing form for flexographic printing.
It is yet another object of the present invention to provide a process for producing the above discussed carrying sleeve for printing and transfer forms. Pursuant to this object, the inventive process includes cutting a base plate corresponding in size to the circumference and breadth of the printing cylinder from thin-walled sheet metal drawn from a roll. Next the base plate is bent into the desired cylindrical form and the edges thereof which are directed toward one another are connected permanently together by a welded seam. The welding is carried out so that a crown is created on the external surface. The entire sleeve surface is processed in order to form a homogeneous, continuous circumferential surface and during this processing the crown is fit into the homogeneous surface.
It is possible to attain the crown of the welded seam in a number of ways. A first possibility is that filler materials can be welded in. In another embodiment the crown is achieved by targeted protective gas feeds. Yet another embodiment of the invention provides the crown by deposit welding which follows the actual welding together of the edges of the plate.
Pursuant to another embodiment of the inventive process, the entire sleeve surface is processed in order to obtain a homogeneous, continuous outer surface. This processing includes chemically roughing and anodizing the hollow cylindrical form of the base plate and subsequently providing the external surface with a photosensitive coating which creates a printing form sleeve suitable for continuous printing. It is desirable to use aluminum as the base plate material.
In yet a further embodiment of the inventive process a metal coat is applied to the processed external surface of the hollow cylindrical form and this metal coat is then mechanically processed. For this it is desirable to use a copper alloy as the metal coat.
Still another embodiment of the inventive process includes applying an endless rubber coating to the entire processed sleeve surface.
Furthermore, it is possible to apply an endless ceramic coat to the entire processed sleeve surface.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.